Operating the self-timer in the 'M' flash synch position will cause the shutter to jam (the instruction book warns not to use the self timer unless the flash sync is set to X, but doesn't warn of the dire consequences of not doing this!), but I'm not aware that it will break the aperture mechanism only. Does the shutter still work?

If you like the camera you could always ask MW Camera Repairs (Google for contact details) for a repair quote, including a good clean of the mirror and screen as these are often quite grubby after 50 years or so. Once fixed and serviced it should go on for years, buying an unknown replacement without guarantee comes with the risk that it could have or soon develop an issue. Hope this is useful and gives you some options to consider.